MnIn2S4 nanosheets growing on rods-like β-MnO2 via covalent bonds as high-performance photocatalyst for boosting Cr(VI) photocatalytic reduction under visible light irradiation: Behavior and mechanism study
2022
Wang, Yingjun | Liu, Yequn | Tian, Fenyang | Bao, Shuangyou | Sun, Chengyue | Yang, Weiwei | Yu, Yongsheng
It is an urgent and onerous task to develop catalysts for photocatalytic reduction of Cr(VI) in wastewater under wide pH range. In this work, a novel hierarchical Z-scheme MnO₂/MnIn₂S₄ (MISO) heterojunction photocatalyst with MnIn₂S₄ nanosheets growing on the surface of β-MnO₂ nanorods is constructed for efficient photocatalytic reduction of Cr(VI). The optimized 2.0-MISO photocatalyst exhibits the almost 100% reduction efficiency in the pH range of 2.1–5.6 under visible light irradiation, and the apparent rate constant is 0.05814 min⁻¹, which is 29.96 and 3.27 times higher than the pure β-MnO₂ and MnIn₂S₄, respectively. A efficient photocatalytic reduction of Cr(VI) to Cr(III) species on 2.0-MISO photocatalyst in actual industry wastewater (286.7 mg/L) up to 99.8% is achieved. Under natural light, the 2.0-MISO photocatalyst also shows rapid reduction of Cr(VI) species. The photocorrosion of MnIn₂S₄ was significantly hindered by the construction of heterojunction. And the O₂⁻ and e⁻ species are the main active species during the Cr(VI) photoreduction process. The connection mode between MnIn₂S₄ and β-MnO₂ is verified by DFT calculations and a possible photocatalytic mechanism is also proposed.
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